This invention relates to a pad for a safety air bag, which may be installed in the steering wheel of an automobile or the like.
Pads of this type usually include an outer covering layer having an upper wall part covering the upper part of the folded air bag and side wall parts extending downward from the periphery of the upper wall part. The upper wall part is normally provided with a break portion which is severed to release the air bag when the air bag is inflated (see Japanese Patent Unexamined Publication No. 199149/1988).
In the pad disclosed in the above-mentioned publication, the portion at which the upper wall part intersects the side wall parts is designed to function as a hinge that allows the upper wall part to outwardly open in the manner of French doors when the break portion is caused to sever by the inflating air bag. The upper wall part pivots about the hinges so that the air bag can be inflated to its full extent on top of the pad.
The side wall parts, the upper wall part, and the hinge part comprising the outer covering of the pad disclosed in the aforementioned pad is made from a soft synthetic resin. The pad includes an insert which is embedded in the outer covering layer and extends from the side wall parts to the break portion on the upper wall part. This insert includes a base part embedded in the side wall parts, lid parts embedded in the upper wall part, and collar parts embedded in the hinges. The collar parts couple the base part with the lid parts and are thinned relative to the insert so that they can flex to permit the upper wall parts to open.
The insert is normally made from a synthetic resin material, which is harder than the synthetic resin material of the outer covering. However, in order to ensure rigidity, the synthetic resin insert must also be relatively thick. As a result, the upper wall part is unable to fully and properly pivot about the hinges, which are formed about the right-angled collar parts. Thus, the opening speed of the upper wall part is inhibited, causing the upper wall part and air bag to open rather unsmoothly.
Accordingly, it is an object of the present invention to overcome the problems stated above by providing a pad for an air bag which allows the upper wall part to open smoothly and rapidly when the air bag inflates, even though a synthetic resin insert is embedded in the pad.